Multimedia over coaxial cable access protocol

ABSTRACT

A BCN network with BCN modems that communicate using predefined messages to establish, optimize and facilitate data communication.

REFERENCE TO EARLIER-FILED APPLICATIONS

This application claims priority under Section 119(e) to U.S.Provisional Application Ser. No. 60/632,856 titled “Interface for aBroadband Coaxial Network,” filed Dec. 2, 2004, which is incorporatedherein, in its entirety, by this reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to broadband communication networks, and inparticular to access protocols used in a local area broadbandcommunication networks.

2. Related Art

The worldwide utilization of external television (“TV”) antennas forreceiving broadcast TV, cable television (CATV), and satellite TV isgrowing at a rapid pace. These TV signals received via an external TVantenna, cable TV and satellite TV, such as a direct broadcast satellite(“DBS”) system, are usually located on the exterior of a building (suchas a home or an office) and enter the building at a point-of-entry(“POE”). Multiple TV receivers, audio video receivers, and/or videomonitor devices may be located within the building and these multipledevices may be in signal communication with the POE via a broadbandcable network that may include a plurality of cables and cablesplitters. Generally, these cable splitters are passive devices anddistribute downstream signals from the POE to various terminals (alsoknown as “nodes”) in the building. The nodes may be various types ofcustomer premise equipment (“CPE”) such as cable converter boxes,televisions, video monitors, cable modems, cable phones, audio videoreceivers, set-top boxes (STBs) and video game consoles.

Within a typical building or home, there may be a mixture of coaxialcables of varying types and quality, such as RG-59, RG-6, and RG-6 quadshield, thus creating a less than optimal RF environment within thecable. Further, typical homes do little or no termination of cableoutlets enabling the introduction of RF interference into the coaxialcables. Another problem often encountered with a typical home orbuilding coaxial cable configuration is the use of multiple splitters ofvarying quality and frequency ranges. This also creates a problem forknown approaches to local area networking over coaxial cable. Suchnetworking often requires a more controlled RF environment or higherquality cabling to support higher frequency ranges.

Typically, an STB connects to a coaxial cable at a wall outlet terminaland receives cable TV and/or satellite TV signals. A device, such as theSTB, connected to the coaxial cable may be called a node. Usually, theSTB receives the cable TV and/or satellite TV signals and converts theminto tuned RF TV signals that may be received by the TV receiver and/orvideo signals that may be received by a video monitor.

In FIG. 1, an example of a known broadband cable network 100 (also knownas a “cable system” and/or “cable wiring”) is shown within a building102 (also known as customer premises) such as a typical home or office.The broadband cable system 100 may be in signal communication with anoptional cable service provider 104, optional broadcast TV station 106,and/or optional DBS satellite 108, via signal path 110, signal path 112and external antenna 114, and signal path 116 and DBS antenna 118,respectively. The broadband cable system 100 also may be in signalcommunication with optional CPEs 120, 122 and 124, via signal paths 126,128 and 130, respectively.

In FIG. 2, another example of a known broadband cable system is shownwithin a building (not shown) such as a typical home. The cable system200 may be in signal communication with a cable provider (not shown),satellite TV dish (not shown), and/or external antenna (not shown) via asignal path 202 such as a main coaxial cable from the building to acable connection switch (not shown) outside of the building. The cablesystem 200 may include a multi-tap device (not shown) that allowscommunication to neighboring homes, a POE to the home 204, N:1 Splitter206, which in this system may also be considered a Root Node,sub-splitter 208, and node devices 210, 212 and 214.

Within the cable system 200, the Multi-Tap (not shown) may be in signalcommunication with the Root Node/main splitter 206 via signal path 228.The Root Node/main splitter 206 may be the connection point from thecable provider that is located externally to the building of the cablesystem 200. The Root Node/main splitter 206 may be implemented as acoaxial cable splitter that may include passive devices and packagesincluding connectors, transformer and/or filters.

The N:1 splitter 206 (a 2:1 splitter in FIG. 2) acts as the mainsplitter and may be in signal communication with N:1 sub-splitter 208 (a2:1 splitter in FIG. 2), and node device 210, via signal paths 230 and232, respectively. The N:1 sub-splitter 208 may be in signalcommunication with node devices 212 and 214 via signal paths 234 and236, respectively. The node devices may be comprised of numerous knownSTB coaxial units such as cable television STBs and/or satellitetelevision STBs, as well as various video and multimedia devicestypically found in the home or office. Typically, the signal paths 228,230, 232, 234, and 236 may be implemented utilizing coaxial cables 216,218, 220, 222 and 224, respectively.

In an example operation, the cable system 200 would receive CATV, cableand/or satellite radio frequency (“RF”) TV signals 226 from theMulti-Tap (not shown) via signal path 216 into the Root Node/mainsplitter 206. The Root Node/main splitter 206 may pass, transform and/orfilter the received RF signals to a second RF signal 230 that may bepassed to N:1 sub-splitter 208 via signal path 218. Sub-splitter 208 maythen split the second RF signal 230 into split RF signals 234 and 236that are passed to node devices 212 and 214 via signal paths 222 and224, respectively. If the node device is an STB, the node device mayconvert the received split RF signal into a baseband signal (not shown)that may be passed to a video monitor (not shown) in signalcommunication with the STB. Similarly, the Root Node/Main Splitterpasses a second signal 232 via signal path 220 to another node device210.

In recent years, numerous consumer electronics appliances and softwareapplications have been developed and continue to be developed that areable to receive, store, process and transmit programming information tomultiple devices in the home at the time and manner as determined by theviewer. The main drawback to the ability of users to view multimediainformation stored on multiple storage devices at the home and view it(or listen to it) on any capable home appliance at the time and mannerof his choosing is the lack of a viable home networking solution. Thereare large numbers and types of CPEs that can be utilized and shared insuch a fashion including televisions, video monitors, cable modems,cable phones, video game consoles, and, audio components, as well asvarious storage devices. There is a growing need for different CPEs tocommunicate between themselves in a network type of environment withinthe building. As an example, users in a home may want to share othertypes of digital data (such as video and/or computer information)between different devices in different rooms of a building.

The present invention is focused on utilizing the home coaxial cable asa medium for high speed home networking by utilizing frequencies abovethe ones currently used by the Cable Operators for their cable service.The home coaxial cable is a natural medium for connecting multimediadevices since it has an enormous amount of available bandwidth requiredfor the high data rates that are needed for such applications and also,all the multimedia devices and appliances are most likely to be alreadyconnected to the coaxial cable. Unfortunately, most broadband cablenetworks (such as the examples shown in both FIG. 1 and FIG. 2)presently utilized within most existing buildings are not configured toallow for networking between CPEs. Most broadband cable networks utilizebroadband cable splitters that are designed to split an incoming signalfrom the POE into numerous split signals that are passed downstream tothe different nodes in different rooms, or equivalently, combine signalsfrom multiple sources (on the “output” ports) to an aggregate on the“input” port. The existing conventional wisdom is that the use ofsplitters in the existing broadband cable networks make these networksable to communicate only between the “point of entry” 204 and nodedevices 210, 212, and 214, and prevents direct networking between nodedevices in the network because signals returning from the node devicescannot be routed back through the splitters, i.e., cannot “jump” asplitter. The present invention describes a system that allows nodedevices (“CPEs”) to communicate directly over the existing coaxial cablewith its current architecture without the need to modify the home cableinfrastructure.

As an example, in a typical home the signal splitters are commonlycoaxial cable splitters that have an input port and multiple outputports. Generally, the input port is known as a common port and theoutput ports are known as tap ports. These types of splitters aregenerally passive devices and may be constructed using lumped elementcircuits with discrete transformers, inductors, capacitors, andresistors and/or using strip-line or microstrip circuits.

Presently many CPEs utilized in modern cable and DBS systems, however,have the ability to transmit as well as receive. If a CPE is capable oftransmitting an upstream signal, the transmitted upstream signal fromthat CPE typically flows through the signal splitters back to the POEand to the cable and/or DBS provider. In this reverse flow direction,the signal splitters function as signal combiners for upstream signalsfrom the CPEs to the POE. Usually, most of the energy from the upstreamsignals is passed from the CPEs to the POE because the splitterstypically have a high level of isolation between the different connectedterminals resulting in significant isolation between the various CPEs.

The isolation creates a difficult environment in which to networkbetween the different CPEs because the isolation results in difficultyfor transmitting two-way communication data between the different CPEs.However, CPEs are becoming increasingly more capable and a growingnumber of users desire to network multiple CPEs to share storage andcapabilities across the network. As CPEs are networked together in thisdifficult environment, the problem of coordinating network resources,accesses and optimizing communications between CPEs becomes a necessity.

Therefore, there is a need for a system and method to connect a varietyof CPEs into a local data network, such as a local area network (“LAN”),within a building such as a home or office, while utilizing an existingcoaxial cable network within the building. Additionally, there is a needfor coordinating network resources, access to the network, and tooptimize the communication between CPEs.

SUMMARY

A Broadband Coaxial Network (BCN) network formed by a plurality ofcommon coaxial network elements that may include passive splitters andcoaxial network nodes where a signal is transmitted from a first BCNmodem to one or more other BCN modems with the signal having multiplepaths caused by reflected signals from the splitters and coaxial networkelements. A Network Controller (NC) BCN modem is established by theactivation of the first BCN modem or when there are multiple devicesthrough a selection process. The other BCN modems in the network thencommunicate with the NC to be admitted to the network and whenattempting to access the network and request transmission opportunitiesto any other node in the network. Each BCN modem communicates with theother BCN modems in the network and establishes the best modulation andother transmission parameters that is optimized and periodically adaptedto the channel between each pair of BCN modems. Further, a bridge may becreated between a first type of network and a second type of network,such as an Ethernet wiring to a coaxial network wiring.

Other systems, methods, features and advantages of the invention will beor will become apparent to one with skill in the art upon examination ofthe following figures and detailed description. It is intended that allsuch additional systems, methods, features and advantages be includedwithin this description, be within the scope of the invention, and beprotected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingfigures. The components in the figures are not necessarily to scale,emphasis instead being placed upon illustrating the principles of theinvention. In the figures, like reference numerals designatecorresponding parts throughout the different views.

FIG. 1 shows a block diagram of an example implementation of a knownbroadband cable system within a building.

FIG. 2 shows a block diagram of another example implementation of aknown broadband cable system within the building shown in FIG. 1.

FIG. 3 shows an example of a BCN network within a home or building andits utilization.

FIG. 4 illustrates two examples of two different architectures for asatellite television system utilizing networking between devices, inthis case, utilizing the Satellite cable to form a network between thedevices.

FIG. 5 illustrates another satellite television bridging approach thatemploys the BCN network of FIG. 3.

FIG. 6 shows a block diagram of a multiple dwelling implementation thatemploys another configuration and utilization of a BCN network.

FIG. 7 shows a block diagram of the BCN network of FIG. 3.

FIG. 8 is an illustration of a functional diagram showing thecommunication between various nodes of a network similar to the oneshown in FIG. 3.

FIG. 9 is another functional diagram showing the interfaces andfunctional relationships between the Nodes of a network similar to theone shown in FIG. 3.

FIG. 10 shows a block diagram of another example implementation andsignal flows of a BCN network

FIG. 11 illustrates another block diagram of another exampleimplementation and signal flows of a BCN network.

FIG. 12 shows a plot of an example bit-loading constellation versusfrequency.

FIG. 13A shows a plot of the bit-loading constellation versus carriernumber for the channel path between node A and node B of FIG. 7.

FIG. 13B shows a plot of the bit-loading constellation versus carriernumber for the channel path between node A and node C shown in FIG. 7.

FIG. 13C shows a plot of the bit-loading constellation versus carriernumber for the resulting broadcast channel path between node A and nodeB and node A and node C based on the constellations shown in FIGS. 13Aand 13B.

FIG. 14 shows an example block diagram of an Ethernet to Coax bridgenode in a BCN network.

FIG. 15 shows a block diagram of one implementation of a multi-portEthernet to coax bridge/router.

FIG. 16 shows a block diagram of an Ethernet bridge/router withadditional WAN and LAN ports including DSL/Cable Modem and wireless.

FIG. 17 is an illustration of various frequency plans for use of the BCNnetwork in different home environments that may include satellite,cable, telco or other services.

FIG. 18 is an illustration of the multimedia access control (MAC) frametypes.

FIG. 19 shows a general format of an example header portion of the MACcontrol/data packet of FIG. 18.

FIG. 20 shows an asynchronous MAP PDU of FIG. 18 with a fixed-lengthPDU.

FIG. 21 is an illustration of an asynchronous MAP PDU header 2100 of theasynchronous MAP PDU of FIG. 18.

FIGS. 22A&B is an illustration asynchronous MAP allocation unit format.

FIG. 23 is an illustration of a NACK allocation unit.

FIG. 24 is an illustration of a reservation request PDU of FIG. 18.

FIG. 25 is an illustration of the format of the request PDU of FIG. 24.

FIG. 26 shows an asynchronous data reservation request element used inthe format of FIG. 25

FIG. 27 is a link probe reservation request element used in the formatof FIG. 25.

FIG. 28 is a link control reservation request element used in the formatof FIG. 25.

FIG. 29 is an illustration of a link probe report PDU of FIG. 18.

FIG. 30 is an illustration of an admission request PDU of FIG. 18.

FIG. 31 is an illustration of an admission response PDU of FIG. 18.

FIG. 32 is an illustration of the format of a key distribution PDU ofFIG. 18.

FIG. 33 is an illustration of the format of the link probe reportrequest PDU of FIG. 18.

FIG. 34 is an illustration of the format of a general linkacknowledgement PDU.

FIG. 35 is an illustration of the link probe C parameters PDU.

FIG. 36 is an illustration of the power adjustment control PDU.

FIG. 37 is an illustration of the power adjustment response PDU.

FIG. 38 is an illustration of the power adjustment acknowledgement PDU.

FIG. 39 is an illustration of the power adjustment update PDU

FIG. 40 is an illustration of an Ethernet data payload of FIG. 18.

FIG. 41 is an illustration of a beacon packet of FIG. 18.

FIG. 42 is a flow diagram of password generation in a BCN network.

DETAILED DESCRIPTION

In the following description of the exemplar embodiments, reference ismade to the accompanying drawings that form a part hereof, and in whichis shown by way of illustration specific embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

Turning to FIG. 3, a diagram 300 of a BCN network within a home orbuilding 302 is shown. A cable/terrestrial network connection 304 ismade at a POE 306 in home 302. The home 302 has a satellite dish 308that may also enter at the POE 306. The satellite dish 308 andcable/terrestrial network 304 may carry data, video, and audio signalsthat may be encoded as analog signals and/or digital signals.

A BCN network 310 within the home 302 connects with the satellite dish308 and cable/terrestrial network 304 at POE 306. The BCN network 310may have connections in different rooms of the home 302, for example, afamily room 312, kitchen 314, office/den 316, master bedroom 318, andkids' bedroom 320. In the family room 312, there may beelectrical/electronics devices such as a home media server 320 (alsodenoted as DVRs such as a personal computer, REPLAYTV or TWO) that maybe connected to a television (i.e., normal television or highdefinition) or video monitor 322. Another type of device in the familyroom 312 connected to the BCN network 310 may be a wireless access point(AP) 324 that communicates with wireless devices such as WebPad 326using a communication standard such as IEEE 802.11 (a, b, and/or g), orBlueTooth, to name but a few communication standards. In the kitchen314, a network audio appliance 328, such as a WMA/MP3 Audio Client, maybe connected to the BCN network 310. Further, a laptop personal computer330 having wireless access ability may communicate with the wireless AP324 located in the family room 312.

The upstairs of home 302 is shown with a media center personal computer332 connected to the BCN network 310 in the office/den 316. The masterbedroom 318 may have a STB 334 that may demodulate an analog or digitalsignal from a cable headend or a satellite receiver connected totelevision or video monitor 336. In the kids' bedroom 320, another STB338 and television or video monitor 340 is shown along with anotherwireless access point 342 connected to the BCN network 310.

The different types of devices connected to the BCN network 310 areprovided as examples of some of the different types of video, data,multimedia, and audio devices that may be typically coupled to the BCNnetwork 310. The BCN network 310 enables two-way communication betweennetwork entities such as the media center personal computer 332 andlaptop personal computer 330 via the wireless AP 324 or 342. The BCNnetwork 310 may also provide streaming multimedia support to transportaudio and video, for example, from the media center PC 332 to theSet-top boxes 334 and/or 338 or any other device connected on the BCNhome network 310.

The BCN network 310 may also connect BCN modems that may be present inthe different devices shown in FIG. 3 in a peer-to-peer mesh network,such that every BCN modem enabled device can communicate directly withany other BCN modem enabled device on the network. Also, in addition tothe peer-to-peer communications, the system can also offer capabilitiesthat may be point-to-multipoint optimized. The BCN modem may be a devicethat communicates across one or more of multiple RF channels where thecommunications over each RF channel by the various devices is divided bytime, where each device transmits in a different time slot, typicallyreferred to as a time division multiple access (TDMA) communication, andeach device transmits or receive at a time denoted as time divisionduplex (TDD), thus enabling one node to transmit at a time into anassigned TDMA frequency channel.

The BCN modem devices may be classified as Intermediate Devices,Terminal Devices, or both, and Operator Service Provider (OSP) Devicesor Non-OSP devices. An intermediate devices device is a device that hasas one of its primary functions bridging of user content between the BCNnetwork 300 and an external device over an industry standard interfacesuch as Ethernet or USB. A Terminal Device is a device whose primaryfunction is to source or sink user content over the BCN network 300.Because an intermediate device functions as a bridge between twointerfaces, and does not know what data services are being bridged,intermediate devices may have throughput requirements while terminaldevices may not. A device may be both an intermediate device and aterminal device.

An Operator-Service Provider (OSP) is an entity that fulfills all of thefollowing requirements of maintaining a WAN infrastructure for deliveryof content directly to consumer's homes such as DBS, HFC, FTTH, xDSL,and wireless, delivers or enables delivery of services (video, audio,voice or data) directly to the consumer's home over such WANinfrastructure, provides significant installation and technical supportto consumers, including live support and maintenance directly to homes,and significantly advertises such installation and technical support.

Some OSPs may choose to use BCN modems to deliver their WAN and/or LANservices into a customer's home. Because the OSP is responsible for thenetwork, an OSP may be permitted to limit BCN modem functionality intheir BCN modems. In particular, the OSP rules ay be:

-   -   OSPs may limit his WAN devices to a single channel and is    -   OSPs are not required to allow sharing of the BCN modem WAN        network with other services or BCN modem devices. However, the        OSP    -   OSPs must enable sharing of the OSPs LAN network with non-OSP        devices.    -   OSPs may limit privacy options as long as non-OSP devices may be        configured to share the LAN network.        Furthermore, OSPs may have different factory default values from        non-OSP devices as long as the non-OSP devices may be configured        to share the LAN network.

In the preferred implementation, the BCN network is a multichannelTDMA/TDD system. Even though there is nothing prohibiting a simultaneoususe of multiple frequencies on the same logical network, most of thedescription that follows assumes that the devices that form the networkare operating on a single frequency channel. Network operation overmultiple frequency channels can be accomplished in several ways. Onemethod can perform transmission opportunities allocations based on bothtime and frequency. In this case, a given BCN node or modem receives itstransmission opportunities on a given frequency channel at a specifictime slot. Similarly, it expects to receive designated packets fromother stations on a given frequency channel at a given time slot.Another method for multiple frequency channels operations is through theutilization of BCN modem bridges that can bridge single frequencychannel networks (or multiple frequency channels networks). It isappreciated by those skilled in the art that the extension of a singlefrequency channel operation to multiple frequency channels operation isknown; therefore this disclosure focuses primarily on a single frequencychannel operation. Due to the unique transmission characteristics of thein-home coaxial network, which may include a highly dispersiveenvironment with very large multipath reflections and a potentiallydifferent channel response between each pair of BCN modems in eitherdirection, the lower network layer of the BCN network 310, denoted asthe physical layer (or PHY layer) may be implemented with a modulationpre-coding (where the modulating waveform is modified to adapt to thechannel in a format that is known to the demodulator in most cases)approach such as adaptive (also denoted as bit-loaded) orthogonalfrequency division multiplexing (OFDM). OFDM is a modulation techniquethat splits the modulated waveform into multiple RF sub-channels, eachof which is modulated by a portion of the data stream and is sent over adifferent subcarrier frequency. With the precoded OFDM technique, thesystem will modulate each of the subcarriers according to thesignal-to-noise ratio of each of the subcarriers.

The physical layer may use a modulation technique such as AdaptiveConstellation Multi-tone (ACMT). ACMT is a form of orthogonal frequencydomain multiplexing (OFDM) where knowledge of the channel is used toselect and optimize the modulation. The modulation automatically adaptsto the channel characteristics to provide the maximum data rate possiblewhile maintaining low Packet Error Rates (PER). The ACMT modulation canvary from 1 to 8 bits per symbol (i.e. BPSK through 256-QAM) dependingon the channel and the capabilities of the node. The term used todescribe the modulation of an ACMT transmission is “modulation profile”.Other precoding methods besides adaptive OFDM may be used in the BCNnetwork 310 with single broadband carrier systems such as Tomlinsonpre-coding or others.

In a typical application, each frequency channel of operation mayconstitute a separate network of communicating devices. It is alsopossible to include a network of multiple frequencies, but the operationof such a network requires rapid frequency changes by BCN modems on apacket-by-packet basis. In a single frequency of operation, one of theBCN modems is assigned as the Network Controller (NC) and provides allthe necessary information allowing other BCN modems to be admitted tothe network, adapt to the network characteristics, synchronize to thenetwork timing and framing, make transmission requests and be able tocommunicate with some or all of the other BCN modems in the network. Inthe current approach, the first BCN modem in the BCN network 310 becomesthe NC by default and the other BCN modems may be referred to as slaveBCN modems. The NC provides network timing synchronization including thetiming of admission area for slave BCN modems. When a BCN modem isactivated, it attempts to locate the network timing by receiving abeacon identifying network timing and essential network controlinformation including network admission area and other informationidentifying the time location and characteristics of other important andvalid information, such as future beacon locations, future channelassignment information, etc. Any BCN modem that wishes to be admitted tothe network then transmits an admission request signal to the NC usingthe identified admission area. If collision occurs in the admission areabetween slave BCN modems, then an appropriate back-off algorithm may beused to resolve the collision and enable the colliding slave BCN modemsto access the admission area at different times. The back-off algorithmmay have the BCN modem wait a predetermined number of beacons. Thepredetermined number of beacons the BCN modem waits may be a randomnumber between 0 and (2^(n)−1), inclusive, where n is the number ofadmission requests sent since receiving the first good beacon, up tomaximum value of n=5. Otherwise admission to the BCN network 310 may beachieved.

Once a new BCN modem establishes its identity and its communicationswith the NC, it may start a network admission process that may includeseveral steps, including the optimization of its communications with theNC based on the channel response characteristics between the BCN modemand the NC in either communications direction, the optimization of thetransmission characteristics between the BCN modem and any of the otherBCN modems already in the network, any calibration requirements toensure adequate communications, etc. Once admitted to the BCN network310, the slave BCN modem can communicate efficiently with every othernode in the network. The NC BCN modem assigns timeslots to the BCN modemto make requests for transmission opportunities to enable thecommunication between the slave BCN modem and each of the other nodes inthe BCN network 310. Once the slave BCN modem contacts another node, thedata path or link between the slave BCN modems and the other nodes maybe optimized. By the end of the admission process, the slave BCN modemknows how to transmit efficiently to every other node in the BCN network310 and subsets of nodes.

In order to manage the BCN network, and control and optimize itsoperation and enable efficient data transmission in the network, severaltypes of data packets may be used to transmit information. The threemost prevalent packet types, for example, are robust packets, probepackets and data transfer packets. The robust packet's maincharacteristics are that it can be received by any BCN modem in thenetwork even before channels are optimized. The robust packets containsignificant redundancy and are transmitted using lower order modulation.The robust packet type is used mainly to broadcast information to allnodes in the BCN network 310 and to enable communications between thembefore the network is optimized, or to communicate most importantcontrol and timing information. One of the robust packets may be calleda beacon that may be sent at anytime, no matter the quality of the link,to provide the basic timing and control information that may be requiredfor robust network operation. The robust packets may also transferoriginal contention and admission information. Another type of robustpacket may be used for influencing hardware, i.e., a global reset of allBCN modems in the BCN network 310.

The probe packet type may be used for at least three functions in a BCNnetwork 310. The first use for the probe packet is link optimization. Anecho profile probe is sent to determine the distance between significantechoes in the network. The determined distances between the echoes areused to calculate the cyclic prefix that is used in messages toaccommodate for the echo and multipath profile of the specific link.

Another probe function may be for hardware calibration. The probe may beused for calibrating the I/Q amplitude and phase Quadrature balance ofthe up and down conversion process. Typical causes for I/Q imbalance arewell known. For example, the phase between the I and Q upconverterand/or downconverter may be off from the optimal 90 degrees, causing anI/Q phase imbalance. Other reasons are unequal signal attenuation and/ordelay between the I and the Q signal paths. One can accommodate lessstringent I/Q hardware requirements by using probe packets for adaptivecalibrations. The probe packet may also be used by requesting a timeslotto be allocated by a NC that may be used by a BCN modem to send packetsto itself or other nodes in order to calibrate parameters and circuits,such as power level, filters, in addition to the I/Q transmissionsignal.

The third type of packet is the data transport packet. The datatransport packet is used to transfer data between nodes in the BCNnetwork 310. These packets are denoted as a MAC packet unit (MPU) andare generally adaptively optimized for each transmission link in orderto achieve the optimal network throughput.

From a communications services point of view, the BCN network providesboth best effort and reserved communications capabilities. It can alsosupport asynchronous and isochronous communications services. In thebest effort services, any packet received by a BCN modem forcommunications over the network requires the BCN modem to make a requestto the NC and receive a time allocation grant to transmit the packet.The BCN modem can make requests for data transmission opportunities formore than one packet but the key characteristics of this operation modeis that transmission requests and grants are made based on a packet ormultiple packet transmission requirements basis and is of a temporarynature; i.e., no long term data transmission allocations commitments areprovided to a BCN modem.

In the reserved mode, certain long-term data transmission requests andgrants are made. In this case, the requests and grants may take severalforms. A common method may be implemented where a BCN modem node makes arequest and is granted a specific allocation for a certain data rate;for example, a BCN modem node may request 10 Mbps channel for a definiteor indefinite duration. In this case, the NC controller (or the network,if the allocation is done in a different manner) may allocate certainpacket transmission opportunities for this node that will amount to theallocated data rate based on the requested data rate. This allocationmay provide for significant time duration until the requested durationexpires, no data being transmitted for a predetermined duration, higherpriority traffic obtaining the required allocation, or any other networkpolicy that may be implemented according to the nature of theallocations and priorities.

Another method for a reserved channel allocation may include a baseallocation (that may be of any size) and additional allocations that maybe based on a flow control method that allows the NC to monitor atransmit buffer at the transmitting node (or other traffic requirementindication) and provide variable transmit opportunities according to thetransmit buffer load or other indicators. In this case, the fixedreserved allocation can support the effective “average” data rate, whilethe additional allocations are able to accommodate temporary data rate“peaks.” That allows a more efficient utilization of the channel,compared to a case where the reserved allocation is required toaccommodate the peak data rate of a given link. Also, even though suchreserved bandwidth is allocated on a “long term” basis, it may bereadjusted very quickly to accommodate potential changes in the trafficprofile.

The NC BCN modem (or the network, in cases where the allocations areperformed in a different manner) may also provide asynchronous andisochronous functionality. Its characteristics are similar to those ofthe best effort and reserved channel communications capability and attimes, the terms are used interchangeably. However, with asynchronousand isochronous functionality, the focus is on the timeliness of theservices. Asynchronous functionality is similar to the best effortcapability discussed above, but the focus is on the indeterminate natureof the timing of delivery. Since this service is in response mostly to apacket delivery that is of random nature, the BCN network does notprovide a tight timing control on the latency of packet delivery throughthe BCN network. Priorities may also be assigned to packets within theBCN network 310 to ensure a priority delivery to certain packets basedon IEEE 802.1p priority tags. Packets of higher priority may havepreference traversing the network as established by a NC policy. Yetanother example of asynchronous functionality may be flow-controlledreservation of timeslots and/or bandwidth for BCN modems.Flow-controlled reservation may include every node being able tocommunicate the status of its transmission buffer status to the NC BCNmodem. The NC BCN modem may give opportunities to transmit even if theother nodes have not requested opportunities for transmission. Anisochronous service is similar to the reserved service but the focus ison a tight control on the delivery time and time variation through thenetwork. Certain communications services, such as MPEG Transport Stream(MPEG-TS) may have tight jitter requirements. In order for the BCNnetwork to support such services, its own communications services needsto be able to limit the delay and delay jitter through the BCN network.This can be done through the assignment of a tightly controlled reservedbandwidth allocation.

As discussed in the above sections, the BCN network may offer bothasynchronous best effort communications services and isochronous,reserved data transport services. An adaptation layer between othercommunications services and the BCN network allows it to provide a widerange of communications services over the BCN network and may beimplemented in the protocol above a MAC layer for transport. Theadaptation layer provides the specific protocol interface to the outsidenetwork and adapts it to BCN network transport. It provides all thenecessary functions to adapt the specific protocol to be transportedover the BCN network. This adaptation may include the same protocol onboth sides of the network or may include protocol conversionfunctionality where one node that may be adapted to one protocol is ableto communicate with another node that may be adapted to anotherprotocol. A simple example may include a device with an Ethernetinterface to a BCN node communicating with a device with a USB interfaceto a BCN node. The adaptation layer may transport other protocols, suchas Ethernet, MPEG Transport Streams, IEEE 1394, and universal serial bus(USB), data over the BCN network. For example, a native MPEG packet froma MPEG transport stream is 188 bytes long and is transmitted with adefined clocking system, so the packets arrive in a predicted fashion.The 188-byte MPEG2 TS packet or multiple MPEG2 TS packets are placed (orencapsulated) in a BCN packet for transmission between BCN modems.Because a MPEG2 TS packet is always 188 bytes, and its timing of arrivalis very well predicted, the bandwidth required in the BCN network 310may be reserved to match the predicted arrival time and thus, such apacket can be transported over the BCN network very efficiently.Additional data, such as timestamps, may be added to the encapsulatedpackets without an impact on that data in order to assure a propertiming transfer resulting in an extremely low jitter. Also, the MPEG2-TSadaptation layer can provide Program ID filtering to select just thedesired programs for delivery over the BCN network.

Another possible adaptation layer is for Ethernet packets. In this case,the adaptation layer may utilize the BCN network asynchronous protocolto transport Ethernet packets over the BCN network. This adaptationlayer may also include the utilization of IEEE 802.1p priorities toprovide a preferential transport to higher priority packets.

A third adaptation layer may include IEEE 1394 transport through the BCNnetwork. In this case, the adaptation layer may utilize both theisochronous, reserved allocations of the BCN network protocol totransport the 1394 isochronous packets and the asynchronous service totransport the asynchronous 1394 packets. Also, it can transport thewhole 1394 transport through the isochronous, reserved allocations. In asimilar fashion, a USB adaptation layer can transport USB packetsthrough the network.

One of the key features of the BCN network is its ability to co-existwith other services over the existing coaxial cable. Such services mayinclude both analog and digital Cable TV services, satellite servicesand/or terrestrial TV services. In order to minimize the potential forinterference by the BCN transmission on the existing services, the BCNmodems in the BCN network 310 may use power control in order to managethe interference generated by and to each of the BCN modems by other BCNmodems and other devices on the network. Nodes or BCN modems that areclose to each other may be subject to a lower attenuation and thusrequire less power to communicate at a given data rate than nodes thatare further apart. The nodes have the ability to adjust transmit poweras communication needs dictate in order to achieve the requiredthroughput with potentially lower transmit power. Thus, the interferencecreated by transmitting nodes is minimized in the BCN network 310without much impact on the total network throughput.

Other power control strategies are also possible. If the network issubject to a significant ingress or other interference from devices inthe BCN network, transmitting to an interfered-with node at maximumpower may overcome the interference. In this case, the network may deemit necessary to slightly increase the probability of interfering withother devices in the network in order to enable more effectivecommunications with interfered-with nodes. Other nodes that may notsuffer the interference may be communicated with only at the nominal orcontrolled power level.

The BCN network is dynamic and allows the occasional additions andremovals of nodes without disruptions of network communications. Eachnode in the network contains a BCN modem. One of the BCN modems usuallyassumes the role of a Network Controller (“NC”) (which may also bereferred to as the Network Coordinator). The NC can be associated with aspecific BCN modem (for example, it can be associated with a networkgateway or a router) or is dynamically assigned according to certainnetwork rules. In a typical application, the NC BCN modem is establishedwhen the first BCN modem is activated in the cable network. In thecurrent implementation, if the NC BCN modem dies or becomes unavailable,a successor takes it place. The successor may be the second BCN modemactivated in the cable network and may monitor a signal from the NC BCNmodem. Or in other implementations, the successor may be predeterminedby a current NC BCN modem based on facts such as link quality with theother BCN modem clients. If the signal is not received for apredetermined amount of time, then the successor becomes an NC for theBCN network 310. If both the first and second BCN modems areunavailable, then either a third designated node (if one exists) maytake over or a hunt for an NC occurs between the slave BCN modems basedon a defined strategy or in a random fashion with the appropriateback-off strategy to resolve conflicts. In other implementations, theslave BCN modem to take over as an NC may be based on random numbersselection, back-off timers, or similar approaches that vary slave BCNmodems determining that an NC is unavailable. This feature may bereferred to as NC mobility.

The NC BCN modem is responsible for managing the BCN network 310. The NCBCN modem manages the other clients' BCN access to the BCN network 310and coordinates assignment of time slots for all BCN modems within a BCNnetwork 310. Additionally, the NC BCN provides synchronization andtiming to the other BCN modems in the BCN network 310.

In another implementation, each new BCN modem wishing to join thenetwork listens to the network on a selected frequency channel to seewhether there is an NC node on the channel. If there is, the new BCNmodem receives the Beacon messages from the NC BCN. The Beacon messagesare very robust and can be received even in a very poor channelenvironment. The Beacon also has information about the admission timeslot for the new node and other network control information. If the newBCN modem is authorized to join the network, the transmit admissionrequest in the admission slot announces its presence to the NC. If morethan one new BCN modem is trying to access the admission time slot, therequest may be unsuccessful and a backup algorithm (a well-knowntechnique) is used for resolution. Once admitted to the network, the newBCN modem continues through the admission process, under the directionof the NC, and communicates with each of the other BCN modems,characterizing each of the possible communication paths to the other BCNmodems. Once the paths to the other BCN modems are characterized, thenthe BCN modem optimizes the communication on each link to maximizetransmission/reception efficiency and quality. Further, each BCN modem(including the NC) may periodically probe all the links to the other BCNmodems and continually make adjustments to maintain the efficiency andquality. Thus, each path or channel between all BCN modems isindividually characterized and optimized, both on admission andperiodically thereafter. Also, if a severe communication interruptionoccurs, the affected node may repeat a process similar to the admissionprocess.

The BCN network may also span across several channel frequencies, wherea single NC may control several frequencies, or each frequency may haveits own NC. In the first case, the NC may control the access to multiplechannel frequencies by controlling not only the time slot allocations ofBCN modems in the network but also their operating frequencies. Anexample of this network may include a NC that controls more than onefrequency channel and may assign communications resources to all the BCNmodems in the frequencies under its control. Such network may includethe assignment of other BCN modems to a given frequency for a certainduration or assign communications resources such as transmission slotsand frequencies on a packet-by-packet basis. All other descriptionsabove are relevant to such an operation as well.

Turning to FIG. 4, a satellite television bridging approach that employsthe BCN network of FIG. 3 is illustrated in cut-away diagram 400. Asatellite LNB+coupler 402 (this may be two or more separate devices thatare connected to each other by signal communication, but is shown hereas a single entity for convenience) receives and down converts asatellite signal from the frequencies transmitted from the satellite tothe antenna (not shown) to frequencies that can be carried over thecoaxial cable 404. The signal is carried by a coaxial cable 404 to aroom 406 having a STB 408 that tunes, demodulates and decodes thesatellite signal into a signal for display on television 410. The STB408 may be equipped to stream a digitally-encoded video show via a BCNmodem located in the STB to another BCN modem in another room. Thestreamed video may be transmitted from the STB 408 to another room 412via the LNB+coupler 402. The streamed video may be received at the slaveBCN modem 414 that is attached to television 416. The slave BCN modem414 communicates with other networking devices, such as a router 418,DSL/Cable Modem 420, and an A/V jukebox 422, using a communicationstandard such as TCP/IP over Ethernet or IEEE 1394 standard. The A/Vjukebox 422 may have a network-attached storage (NAS) 424. The router418 may be connected to a personal computer 426 that communicates via aUSB connection with a printer 428.

The satellite signal is received at the LNB+coupler 402 and is thentransmitted via the coaxial cable 404 to the STB 408. The STB 408 has1+N tuners/receivers used to select desired channels. The channelreceived by the first tuner is demodulated, decoded and is shown on theconnected TV (or monitor) 410. The other N tuners may each select achannel and demodulate and decode the signal received at the selectedchannel as a digital video data stream. The data stream is carried bythe BCN network back through the LNB+coupler 402 to the device havingthe slave BCN modem located in another room 412 for display ontelevision 406 or through the router 418 to be displayed on the personalcomputer 426. Such transmission of data between devices and rooms mayoccur to any number of rooms, provided another BCN modem is present onthe BCN network in the other rooms. Transmission may be point-to-pointor point-to-multipoint. The LNB+coupler 402 provides the means ofcommunication between the various cables 404 connected to it at acertain frequency band or several frequency bands that do not interferewith other signals on these cables. Such frequencies may include bothbaseband frequencies and RF frequencies.

In FIG. 5, another satellite television bridging approach that employsthe BCN network of FIG. 3 is illustrated in cut-away diagram 500. Acable 502 from a satellite antenna is coupled to a STB 504 having 1+Ntuners/receivers. The STB 504 may have a second connection via a BCNmodem to the BCN network 310 via cable 506 and cable television (CATV)drop 508. The BCN network 310 has outlets in other rooms, such as 412.

In this implementation, the satellite signal is received at the STB viacable 502. At least one of the 1+N tuners converts the signal into avideo signal for display on a local television 410. The other Ntuner/receivers tune and demodulate other possible channels where any,some or all demodulated data are then encoded into one or more digitalstreams and transmitted across the BCN network 310 by the BCN modemenabled device. The digital stream is then received in another room 412at a device having another BCN modem. The digital stream is thenconverted and/or RF modulated for display on a television 416 ordirectly streamed to a personal computer 426. Even though digitalstreaming of video is used here to demonstrate data transmission acrossa BCN network, other types of data may be exchanged to transmit and/orreceive.

Turning to FIG. 6, a block diagram 600 of a multiple dwelling unit(“MDU”) application that employs the BCN network is shown. It is oftendesirable to provide office buildings and apartment/condominiumdevelopments with cost effective data and video services. Such a systemmay be referred to as an “access type” implementation and is describedwith a cable television (CATV) headend 602 being a source for receptionof video transmission from a provider of video services and connectionto other two-way networks for data and video. The CATV headend 602 mayhave a fiber optical encoder 604 that encodes a single or multipleanalog or digital video signals onto an optical physical transportmedium, such as multimode fiber-optic cable 606. The headend 602 mayalso have an Ethernet to passive optical network (“E-PON”) transceiver608 that converts Ethernet data for transmission over a fiber-opticcable 610. The fiber-optic cables 606 and 610 may be terminated at ahybrid fiber-optic cable (“HFC”) node 612.

The HFC node 612 may have an Optical to Electrical converter 614 todecode the received video signal for transmission over a coaxial cable616. The coaxial cable 616 may have one or more amplifiers 618 tomaintain the necessary transmitted signal strength range along thecoaxial distribution. A passive optical network (“PON”) splitter 620 maysplit the optical signal to multiple location terminations, e.g., 16terminations.

At least two different access implementation examples in a MDU are shownwhere data may be supplied by fiber-optic cable to the MDU anddistributed to the different units on the coaxial cable typically usedfor video services, such as cable television distribution. The firstexample, referred to as “Type A MDU” dwelling 622, has a POE 624 to thedwelling 622. The coaxial cable within the dwelling 622 forms the BCNnetwork 623. Often within the dwelling 622, one or more amplifiers 626,628 are installed along with one or more passive splitters 630 to formthe BCN network 623. The BCN network 623 is connected to BCN modems 632,634, and 636 that enable Ethernet traffic to be carried over the BCNnetwork 623. The BCN modem 632 may be connected to a personal computer(PC) 638, as BCN modem 634 is connected to PC 640, and BCN modem 636 toPC 642. The BCN network may also carry analog or digital video signalsto set-top boxes 644, 646, and 648 that may be connected to televisions650, 652, and 654, respectively.

The BCN network 623 is connected to the Internet via a BCN modem enabledEthernet hub 656 that is shown connected to an optical network unit(ONU) 658 that functions as a transceiver on the fiber-optic cable 660connected to PON 620. Thus downstream video and audio signals aretransmitted via the HFC node 612 to the dwelling 622. A two-way datapath exists from the ONU 658 to the E-PON 608 located at the headend602.

The “Type A” MDU implementation enables multiple units, e.g., 32 unitsin the example embodiment, to share the BCN modem enabled Ethernet hub656 and ONU 658. The communication between devices, such as PCs 638 and640 in the “Type A” implementation, flows through the PON 620 andheadend 602. This is in contrast to the single home BCN network, shownin FIG. 3, where devices within the home communicate directly with eachother.

In the other implementation example, “Type B” MDU 661 has a coaxialcable POE 662 connected to the internal coaxial network 663. Theinternal coaxial network 663 may have passive elements such as splitters664. The coaxial network 663 may have BCN modems 670 and 672 connectedto PCs 674 and 676, respectively, or other Ethernet enabled devices. TheBCN modems 670 and 672 communicate with the BCN modem enabled hub 673that is coupled to the ONU 675 for bi-directional communication with thePON 620 via a fiber optical cable 677. One or more STBs, such as 678,may be connected to televisions, such as 680, and the coaxial network663. Unlike the “Type A” MDU 622 implementation, the “Type B” MDU 661implementation has some units with access to the BCN Modem enabled hub673 while others only receive the traditional features provided by acable company.

Within either the “Type A” or Type B″ MDU implementations, the coaxialcable may employ a frequency plan 690 that uses 50-770 MHz 692 forbroadcasting of video and audio signals. Another area of the frequencyplan 690 employs a 50 MHz bandwidth 694 at approximately 900 MHz for useby the BCN modems. The upper end of the frequency band 1030 MHz-1450 MHz696 may be used by satellite television systems, such as DIRECTV.

The BCN modems are able to create a BCN network while supportingfeatures such as high definition television, Dolby 5.1 digital audio,parental control systems, return channels (remote or interactivetelevision), and Internet data. They enable CPE devices that are TCP/IPenabled, or utilize other protocols, to communicate across the BCNnetwork by communicating with a BCN modem that receives the data via acommunication protocol, such as TCP/IP, and converts the TCP/IP signalinto a signal for transmission across the BCN network.

The BCN modems may also use encryption algorithms to encrypt data to betransmitted across the BCN network. The transmitted data is thendecrypted at the receiving BCN modem for delivery to another CPE. Theencryption may be DES based or use other encryption algorithms such asIP-SEC, etc. Various keying systems can be used and the various keyingmethods are well established in various standards, such as IEEE 802.11,Docsis, and others, and need not be detailed herein.

In FIG. 7, a block diagram 700 of a BCN network similar to that of FIG.3 is shown. The coaxial cable 304 enters the premises at the POE 306.One or more passive splitters, such as passive splitter 722 may be inthe BCN network 310, FIG. 3. The splitter 722 splits the signals incoaxial cable 730 into multiple coaxial cable lines 732, 734, and 736.The coaxial cable line 732 is coupled to Node A 724, coaxial cable line734 is coupled to Node B 726, and coaxial cable line 736 is coupled toNode C 728. Each Node may have a BCN modem that transmits and receivesTCP/IP (or other protocols) data over their respective coaxial cablelines 732, 734, or 736. The BCN modem also converts the data from/to aphysical layer and link layers transmitted on the twisted pair Ethernetcable lines 710, 712, and 714, to the BCN network. The cable lines 710,712 and 714 may also be USB cables, IEEE 1394 cables or any othercommunication connections, including printed circuit board communicationlines or even communication wires inside integrated circuits. Thesecable lines represent any communications methods, including all layersof the communications protocol, which are then translated at Nodes A724, B 726, and C 728, prior to transmission over the BCN network. EachCPE 704, 706, and 708 may be connected to an Ethernet cable 710, 712,and 714, respectively (or other communications methods). The differentCPEs 704, 706 and 708 may communicate over the BCN network across thesplitter 722.

In FIG. 8, a functional diagram 800 showing the logical communicationbetween various nodes, Node A 724, Node B 726, Node C 728, and Node D808, in the form of a virtual logical mesh network is shown. The nodes724, 726, 728, and 808 may be interconnected between node pairsutilizing corresponding inter-node channels between the node pairs. Itis appreciated by those skilled in the art that even if the nodes areindividually connected with one another via a single inter-node channelbetween the node pairs, each inter-node channel between node pairs maybe asymmetric. Therefore, inter-node channels between Node A 724, Node B726, Node C 728 and Node D 808 may be asymmetric and may requiredifferent modulation schemes for optimizing the specific link. Suchoptimization may be a different bit-loading scheme in an OFDM-basedcommunications system or some other optimized method that optimizes thecommunications based on the specific channel available, which may bedifferent on one physical link, depending on the direction of thesignals between the nodes. As a result, the typically asymmetricinter-node channels between Node A 724, Node B 726, Node C 728, and NodeD 808 may be described by the corresponding direction-dependent nodechannels AB, BA, AC, CA, BC, CB, AD, DA, BD, DB, CD, and DC.

As an example, Node A 724 is in signal communication with Node B 726 viasignal paths 810 and 812. Signal path 812 corresponds to the AB channeland signal path 810 corresponds to the BA channel. Additionally, Node A724 is also in signal communication with Node C 728 via signal paths 822and 824. Signal path 822 corresponds to the AC channel and signal path824 corresponds to the CA channel. Similarly, Node B 726 is also insignal communication with Node C 728 via signal paths 802 and 804.Signal path 804 corresponds to the BC channel and signal path 802corresponds to the CB channel.

In this example, the AB channel corresponds to the channel utilized byNode A 724 transmitting to Node B 726 along signal path 812. The BAchannel corresponds to the reverse channel utilized by Node B 726transmitting to Node A 724 along signal path 810. Similarly, the ACchannel corresponds to the channel utilized by Node A 724 transmittingto Node C 728 along signal path 822. The CA channel corresponds to thereverse channel utilized by Node C 728 transmitting to Node A 724 alongsignal path 824.

Because all links are individually optimized to maximize the throughputon each link, a multicast or a broadcast transmission is problematic. Inan example of operation, in order for Node A 724 to transmit the samemessage to both Node B 726 and Node C 728 using the AB channel alongsignal path 812 and the AC channel along signal path 822, Node A 724 mayneed to transmit (i.e., “unicast”) the same message twice, once to NodeB 726 and a second time to Node C 728 if the channel pre-coding makesthe optimized signal waveform on the AC channel quite different fromthat of the AB channel. Since the nature of communicating on the networkmay include a significant percentage of multicast/broadcastcommunications, this may have a significant impact on network efficiencyif similar messages need to be repeated on each optimized link.

To maximize the network efficiency even for multicast and broadcasttraffic profiles, each of the nodes utilizes the individual linkoptimization into a combined link optimization as follows; when a node,such as Node A, joins the network, it optimizes its transmission to eachof the other nodes in the network. This optimized link is stored in thenode's storage. Once a node wishes to transmit a certain message tomultiple other nodes, it may do it by repeating the message multipletimes or computing an optimal “multicast” transmission profile from theindividual profiles in its memory. The node may also utilize a hybridscheme if a better throughput can be achieved. In such a hybrid scheme,the node may decide to break the nodes it wishes to send the samemessage to into subsets of nodes that may share largely similar channelcharacteristics. Each of these subsets will utilize a specificallyoptimized channel transmission and the same message will be transmittedto all such subset groups. In actual operation, it may be that mostmessaging will be unicast or broadcast, so that in addition to theindividually optimized transmission to each of the other nodes in thenetwork, only a broadcast optimized transmission may be necessary. Thepreferred implementation of the optimized multicast or broadcast schemein the proposed network takes advantage of the preferred bit-loaded OFDMscheme and utilizes a combined bit-loading for the subset of thechannels to which a node wants to send the common message. This methodis described further in the following sections.

The network topology shown in FIG. 8 is a full-mesh peer-to-peernetwork. The BCN modem may utilize other forms of network topology,which may include a partial-mesh network, a star network, or acombination thereof. Because in a star network, communications arealways between a central node and the network nodes only, the optimizedtransmission is performed between the central node and the other networknodes only, and in the preferred optimization, the bit-loading scheme isestablished between the central node device acting as the NC and each ofthe remaining nodes in the network.

The BCN modems may automatically be configured as either a NC or a slaveduring startup. Each BCN modem is capable of transmitting and receivingon a selected control and/or broadcast channel using what is commonlyreferred to as precoding. The selected broadcast channel is selected asa channel having sufficient quality to enable all BCN modems tocommunicate with the NC.

If a BCN modem is started and it does not detect a control channel witha NC BCN modem, then it assumes the role of a NC. Otherwise a NC BCNmodem is detected and the BCN modem starting up is configured as a slaveBCN modem. For example, when Node A 724 starts up first and assumes therole of NC, the other Nodes B 726 and Node C 728 start up later as slaveBCN modems. If two or more BCN modem start up at the same time, a randomback-off timer may be used to stagger the establishment of a NC BCNmodem. Further, if the network is divided, a BCN modem slave willdetermine that no NC is present and assume the role of the NC.

Once a NC, such as Node A, is established, the quality of the data pathsto and between the other nodes is determined. There may be multiplecommunications paths between Node A and the other nodes due to thesignal reflections that may occur at splitters and other networkconnections. The data paths for communication between selected nodes aredetermined and the paths between one node to multiple nodes commonlycalled multicast are determined. It may not be true that the best signalquality path for a pair of nodes will be the best quality for amulticast to the pair of nodes and one or more other nodes. Often theremay be a common channel that has an acceptable quality for all the nodesinvolved in the multicast.

The multicasting is typically setup at the link layer of the protocolwith a multicast group and members join and leave the group as required.A multicast address translation protocol may map up to 64 multicastchannels to unique BCN modem channels. Further, either the NC or slaveBCN modem may initiate a multicast session.

In FIG. 9, another functional diagram 900 showing the interfaces andfunctional relationships between the Nodes of FIG. 3 is shown. In thisdiagram, Node A 724 may transmit a message in broadcast or multicastmode simultaneously to Node B 726 and Node C 728 channel via signalpaths 812 and 822, respectively. When the network was established, NodeA 724 had optimized its communications with Node B 726 as channel AB.Also, Node A 724 optimized its communications with Node C 728 as channelAC. If Node A 724 needs to transmit a message to Node B 726 or Node C728, it utilizes the optimized transmission for channel AB or channelAC, respectively. However, once Node A 724 wishes to transmit a messageto both Node B 726 and Node C 728 simultaneously, it may not be able todo it effectively if the optimized transmissions for channel AB andchannel AC are different. Node A 724 may transmit the message twice,once to Node B 726 with an optimized transmission to channel AB, andonce to Node C 728, with an optimized transmission to channel AC.However, analysis has shown that there is a better and more efficientway to transmit the same message to both Nodes B 726 and C 728. Node A724 can optimize the transmission to a new channel denoted as channelA-BC. This optimized transmission may be the best transmission formessages destined to both Nodes B 726 and C 728. Extensive analysis onmodels of real cable systems have shown that in most cases, such methodis preferred and yields a better throughput compared to repeating themessage for optimized channels AB and AC. In the implementationdiscussed herein, the optimization for channel A-BC is relativelystraightforward. Because each of the optimizations for channel AB andchannel AC are done by bit-loading according to the frequency responsesof paths 812 and 822, channel A-BC optimized transmission is the onethat optimizes the bit-loading for the combined response of paths 812and 813.

It is appreciated by those skilled in the art that the differentchannels typically utilize different bit-loading modulation schemes,because the channels typically are physically and electrically differentin the BCN network. Physically the channels often vary in length betweennodes and electrically vary because of the paths through and thereflections from the various cables, switches, terminals, connections,and other electrical components in the BCN network. A bit-loading schemeis described in U.S. Utility application Ser. No. 10/322,834 titled“Broadband Network for Coaxial Cable Using Multi-carrier Modulation,”filed Dec. 18, 2002, which is incorporated herein, in its entirety, bythis reference.

In another implementation, the BCN network may operate with waveformsthat utilize bit-loaded orthogonal frequency division multiplexing(OFDM). Therefore, the BCN network may transmit multiple carrier signalswith different QAM constellations on each carrier. As an example, over abandwidth of about 50 MHz, the BCN network may have 256 differentcarriers that in the best circumstances would utilize up to 256 QAMmodulations. However, the modulation of each carrier may be adjustedaccording to the specific channel response. If at certain frequencies,the response is poor, the BCN network may utilize BPSK or a low orderQAM for carriers in those frequencies. If the channel is good in someother frequencies, then a high order QAM can be utilized on thosefrequencies, which is the essence of bit-loading optimization.

The application of bit-loading in a BCN network is demonstrated in FIG.10. As an example, in FIG. 10, a block diagram of the BCN network 700 ofFIG. 7 is shown. The BCN network 700 may be in signal communication witha cable provider (not shown), satellite TV dish (not shown), and/orexternal antenna (not shown) via a signal path 304, such as a maincoaxial cable from the customer premises to a cable connection switch(not shown) outside of the customer premises.

The BCN network 700 may include the POE 306 and splitter network 722that has a main splitter 1006, a sub-splitter 1008, Nodes A 724, B 726and C 728, and STBs A 1016, B 1018 and C 1020. Within the BCN network700, the POE 306 may be in signal communication with the main splitter1006 via signal path 1022. The POE 306 may be implemented as a coaxialcable connector, transformer and/or filter.

The main splitter 1006 may be in signal communication with sub-splitter1008 and Node C 728 via signal paths 1024 and 1026, respectively. Thesub-splitter 1008 may be in signal communication with Node A 724 andNode B 726 via signal paths 1028 and 1030, respectively. The mainsplitter 1006 and sub-splitter 1008 may be implemented as coaxial cablesplitters. Node A 724 may be in signal communication with STB A 1016 viasignal path 1028. Similarly, Node B 726 may be in signal communicationwith STB B 1018 via signal path 1030. Moreover, Node C 728 may be insignal communication with STB C 1020 via signal path 1026. STBs A 1016,B 1018 and C 1020 may be implemented by numerous well known STB coaxialunits, such as cable television set-top boxes and/or satellitetelevision set-top boxes. Typically, the signal paths 304, 1022, 1024,1026, 1028, 1030, 1032, 1034, and 1036 may be implemented utilizingcoaxial cables.

As an example of operation, if STB A 1016 transmits a message to STB B1018, the message will propagate through at least two transmission pathsfrom Node A 724 to Node B 726. The first transmission path 1040 travelsfrom Node A 724 through signal path 1028, leakage between output portsin sub-splitter 1008, and signal path 1030 to Node B 726. The secondtransmission path includes transmission sub-paths 1042 and 1044. Thefirst sub-path 1042 travels from Node A 724 through signal path 1028,sub-splitter 1008, signal path 1024, main splitter 1006, and signal path1022 to POE 306. The message may reflect due to less than idealtermination at the input or output of the POE 306 and go back throughthe second sub-path 1044. The second sub-path 1044 travels from POE 306,through signal path 1022, main splitter 1006, signal path 1024,sub-splitter 1008, and signal path 1030.

The first transmission path 1040 typically tends to experience a certainattenuation because of the isolation between the output ports ofsub-splitter 1008. The second transmission path 1042 attenuation resultsmostly from the reflection at the POE 306 due primarily to impedancemismatches between the input or output of POE 306 and the rest of theBCN network 700. Of course, there may be additional paths the signal cantravel through due to other reflections in the various paths of the BCNnetwork 700. The result of all these multiple transmission paths is apotentially extensive dispersive channel between STB A 1016 and STB B1018. This channel, however, is fairly static and does not changerapidly.

As another example, in FIG. 11, the communications between STB A 1016and STB C 1020 is described for the BCN network of FIG. 10. In thisexample of operation, if STB A 1016 transmits a message to STB C 1020,the message will propagate through two or more transmission paths fromNode A 724 to Node C 728. Two transmission paths of this example areshown in FIG. 11. The first transmission path 1040 travels from Node A724 through signal path 1028, sub-splitter 1008, signal path 1024, andsignal path 1026 to Node C 728, with leakage between the output ports ofthe main splitter 1006. A second transmission path includes transmissionsub-paths 1042 and 1044 and the reflection at the input and/or theoutput of the POE 306.

In the example of FIG. 11, it is to be expected that the dispersal maybe of a different nature than that of FIG. 10 because the leakagethrough the main splitter 1006 output ports is likely to be differentcompared to the leakage between the output ports of the sub-splitter1008, and the difference in path lengths between the two transmissionpaths in the example of FIG. 11 is likely to be smaller because itincludes only the traversing of the path 1022 twice, once on the way tothe POE 306 and once on the way back. In contrast, in the example ofFIG. 10, the difference in the paths includes the traversing twice ofboth the 1022 and 1024 paths.

In FIG. 12, a plot 1200 of the frequency response of the Node A to NodeB 1208 two transmission path and the Node A to Node C 1206 twotransmission path is shown. In both channels, the two transmission pathshave similar attenuation, resulting in a frequency response with deepnotches. This occurs at frequencies where the phase difference throughthe two paths is 180 degrees, resulting in the cancellation of thesignal because their amplitude is identical. It may be noted that thefrequency response of the Node A to Node B 1208 transmission pathcontains more notches per unit frequency than the Node A to Node C 1306transmission path because its path time difference is larger. Similarly,because the time difference between the two paths of the Node A to NodeC channel is smaller, the frequency difference between the notches inits frequency response is larger, as should be expected. Thus, FIG. 12illustrates that in order to communicate between Node A and Node B, orbetween Node A and Node C, a special waveform may be required in orderto deal effectively with the respective channels. Moreover, thesechannel responses are likely to be different in different cable systemsand also are likely to change in time due to a change in configuration,such as when a user may add new devices to his cable system or changeits topology, or due to slowly occurring changes caused by aging orchanges in temperature or humidity that can change the leakage throughthe devices. Hence, the transmission system needs to constantly adapt tochanging channel conditions.

In the example implementation, such adaptation is performed through atechnique of OFDM modulation combined with an optimized bit-loading. Inan OFDM optimized bit-loading, the modulation for each carrier isadapted to the channel response and noise (and interference) at thecarrier frequency. FIG. 12 shows an example of bit-loading constellation1202 versus frequency 1204 for the channel path utilized by Node A totransmit to Node B 1208 and the channel path utilized by node A totransmit to Node C 1206. Line 1208 represents the AB channel and line1206 represents the AC channel. As can be seen from FIG. 12, atfrequencies where the frequency response provides good transmission pathand depending on the noise level, the BCN network may utilize high ordermodulation to permit better throughput at these frequencies. Themodulation axis 1202 shows the QAM level (16, 32, 64 . . . 256)corresponding to a given frequency response level 1206 and 1208 at agiven frequency 1204. Around the notch frequencies 1212 and 1214 of theresponse 1208 and 1210 of the response 1206, nothing at all may betransmitted because the notch is very deep. Sufficient margin may beprovided to ensure that the selected modulation provides the necessaryBit Error Rate (“BER”) and allows for small changes in the response.Additional QAM levels such as 2-QAM, also known as BPSK, and 4-QAM, alsoknown as QPSK, can be used but are not shown in FIG. 12.

Returning to FIG. 9, the BCN network 900, in order to ensure that bothNode B 726 and Node C 728 are able to receive a broadcast signaltransmitted from Node A 724, utilizes a bit-loading modulation schemethat is known as the common bit-loaded modulation scheme. The commonbit-loaded modulation scheme transmitted via the A-BC channel, alongsignal path 902, is a combination of the bit-loading modulation schemetransmitted via the AB channel, along signal path 812, and the ACchannel, along signal path 822.

FIGS. 13A, 13B and 13C provide examples of common bit-loading. In FIG.13A, a plot 1300 of carrier frequency signals of various bit-loadingconstellations 1302 versus carrier number 1304 for the AB channel pathsuch as that of FIG. 9 between Node A and Node B is shown. Line 1306represents the AB channel frequency response and a correspondingenvelope of the constellation sizes of 8 different carrier signalsnumbered 1-8 within the transmission signal for the AB channel. In theexample, within the AB channel the transmitted OFDM signal includes theindividual carriers with different modulation constellations, such ascarrier number signals 1 and 8 that may transmit at a constellation sizeof 256 QAM, carrier number signals 2, 3 and 7 that may transmit at aconstellation size of 128 QAM, carrier number signals 4 and 6 that maytransmit at a constellation size of 64 QAM, and carrier number signal 5that may be OFF (i.e., no carrier signal may be transmitted because ofthe null in the channel response).

Similarly in FIG. 13B, a plot 1308 of a frequency response 1314 and thecorresponding bit loading scheme 1310 vs. frequency 1312 for the OFDMcarrier frequency signals for the AC channel such as that of FIG. 9 isshown. Again, line 1314 represents the AC channel response and there isa corresponding envelope of the constellation sizes of the 8 differentcarrier number signals within the AC channel. As an example, within theAC channel, carrier number signals 1, 2, 4, 6 and 8 may transmit at aconstellation size of 128 QAM, carrier number signal 5 may transmit at aconstellation size of 256 QAM, and carrier number signals 3 and 7 may beOFF (again, no carrier signals may be transmitted because of nulls inthe channel response).

In FIG. 13C, a plot 1316 shows the common bit-loading scheme of the OFDMcarrier constellations 1318 versus carrier number 1320 for broadcastingmessages over the A-BC channel path between Node A and Nodes B and C. Inthis example, plot 1316 shows that within the A-BC channel, an OFDMsignal consisting of carrier number signals 1, 2, and 8 may transmit ata constellation size of 128 QAM, carrier number signals 4 and 6 maytransmit at a constellation size of 64 QAM, and carrier number signals3, 5, and 7 are OFF. These carrier number signal values are the resultof comparing the carrier number signals from the AB channel in FIG. 13Aand the corresponding carrier number signals from the AC channel in FIG.13B and choosing the lowest corresponding modulation value for eachcarrier number. The resulting common carrier frequency signals in FIG.13C graphically represent signals utilizing the common bit-loadedmodulation scheme. These signals would be able to transmit informationfrom Node A to Node B and Node C simultaneously.

Turning to FIG. 14, a block diagram of an Ethernet bridge node of theBCN network 700 for FIG. 7 or FIG. 3 is shown. The BCN network cable1402 may be connected to a standard coaxial cable wall plate 1404, suchas those made by LEVITON. The coaxial wall plate 1404 may secure to thecable 1402 via a connector, such as a F-type or BNC connector. Typicallythe cable may be 75-ohm RG-59, some type of RG-6, or a combination ofsuch 75-ohm cables. The Ethernet to Coax Bridge Device 1400 may have adiplexer 1408 that passes the RF frequencies below 860 MHz to a cable1410 that may be connected to a video type device (not shown), such as atelevision, VCR, Audio/Visual Receiver, or television tuner PC card.

The Ethernet to Coax Bridge Device 1400 may have a BCN modem 1406 thatconnects to a BCN network such as that shown in FIG. 3 and FIG. 7, andthat enables it to code and decode messages between connected devicessuch as a wireless access point 1412, media server 1414 or a networkattached storage 1416 for transport across the BCN network through thecable 1402. The various devices wishing to communicate over the BCNNetwork to other devices in other bedrooms communicate by using standardEthernet packets. The Ethernet to Coax Bridge (ECB) provides Ethernetbridging, switching and/or routing functions for all connected devicesto other devices connected over the BCN network. Hence, a laptop (notshown) may be connected wirelessly to the Wireless AP 1412. The WirelessAP 1412 may route the Laptop packets to other devices connected to theECB or through the BCN Network, to other devices in other rooms that areconnected to the BCN Network through other ECBs, or directly to STBs,PCs, TVs, gateway and any other device that is capable of communicationsover the BCN network through a BCN modem. Similarly, the Media Server1414 may communicate through the ECB to TV sets, other Media Servers orMedia Extenders connected to the BCN Network in any room. The ECB mayoperate a bridge, switch and or router over an Ethernet network.However, its functionality spans not only any Ethernet segment it isconnected to but also across the full BCN Network, providing a fullLayer 2 and upper layers functionality across the whole BCN network andother networks through gateways. Due to the capabilities of the BCNNetwork, the ECBs may provide high levels of Quality of Service (“QOS”),including network wide priorities such as IEEE 802.1p, and even higherlevel of QOS services including prioritized flow control for selectedflow across the network. These capabilities are inherent in the BCNNetwork and may be utilized by all the devices connected to the BCNNetwork including ECBs.

In FIG. 15, a cable home gateway/router node 1500 is shown. The cablehome gateway/router node 1500 is connected to BCN network by a cable1502. The cable home gateway/router node 1500 may have a diplexer 1504that passes RF frequencies below 860 MHz to another cable 1506 that maybe connected to a video type device or any other cable device thatutilizes frequencies below 860 MHz, such as a STB, TV set, cable modem,etc. A BCN modem 1508 may be connected to BCN network cable 1502 via thediplexer 1504. The BCN modem 1508 may also be connected to a networkprocessor/CPU 1510, such as a host microprocessor, digital signalprocessor, or other known digital controllers by an electrical bus, suchas a PCI bus 1509 or any other internal or external parallel or serialhigh speed bus.

The Network Processor/CPU 1510 may be configured to support WANconnectivity, such as the Docsis cable modem communication standard fordata communication with a cable head end or DSL, dial-up connection, orWireless Access through a WAN port. This port may or may not support MACfunctions, but may transmit and receive WAN Packet Data Units to the WANport 1524. Further, the Network Processor/CPU may support otherconnections, such as USB 1.0, USB2.0, or other networking technologies.A N-port switch (4-port shown) 1512 may also be incorporated into thecable home gateway node/router 1500. The ports 1514, 1516, 1518, and1520 (typically called local area network ports) may be coupled toEthernet network devices (not shown). The cable home gateway/router node1500 may also provide multiple networking functions, including gatewayfunctions, e.g., WAN to/from LAN packet transmission and protocolconversions, LAN switching and/or routing functions and protocolconversions between the multiple LAN and WAN functions, which mayinclude one or more BCN networks.

Turning to FIG. 16, an integrated Ethernet bridge/router with integratedWAN modems (“IEBR”) 1600 is shown. In this example implementation, thefunctionality and options of the bridge/router of FIG. 15 are integratedwith the functionality of cable modem and/or DSL and/or wireless access,and also with wireless LAN connectivity as additional local ports. A BCNnetwork cable 1602 is connected to a triplexer 1604 that may pass RFfrequencies less than 860 MHz on another cable 1606 to a video device(not shown). The triplexer 1604 may also be coupled to a Docsis cablemodem 1610 and a BCN modem 1612. The IEBR 1600 also may have a DSL modemthat interfaces to a telephone line (not shown) and also to a wirelessWAN access modem 1608. The IEBR 1600 may also be connected to a networkprocessor 1614 and support an N-port switch (4-port switch shown) 1616and a wireless LAN 1609. Each of the ports of the N-port switch may beconnected to an Ethernet enabled device, such as a media server/PC 1622.The media server/PC 1622 may also be connected to the other cable 1606.The functionality of the integrated router/WAN modem is similar to thatof FIG. 15 but is integrated with the WAN modems and a wireless LAN.

In FIG. 17, a diagram 1700 of frequency plans is illustrated. In mosttwo-way cable systems 1702, an upstream frequency band is located in the5-42 MHz frequency band 1704. Analog and digital cable televisionsignals and cable modem downstream carriers are found in the 50-860 MHzfrequency band 1706 and the BCN network 1708 is located between 940-1400MHz. In theory, the BCN network can be located above 860 MHz, but inorder to allow diplexers in systems that may require it, it may beprudent to allow a certain frequency band for the filters roll-off. Adifferent implementation, such as the network shown in FIG. 4 or onewhere the BCN network is not connected to cable at all and is availableexclusively for satellite use, is shown in FIG. 17, 1710. In thisimplementation, the BCN network 1712 may be located between 2-38 MHz andoff-air signals 1714 between 50-806 MHz. The Satellite L-Band 1716 maybe located between 950-2150 MHz. In yet another implementation 1718, thesystem operates on a BCN Cable Network that is capable of providing bothsatellite and cable services. In this case, the cable upstream frequencyband 1720 may be present between 5-42 MHz, the cable TV signals between50-860 MHz 1722, the BCN network 1724 in a frequency band found between880 and 940 MHz, and satellite L-band 1726 located between 950-2150 MHz.The final implementation 1728 demonstrates the application over cablesystems where two or more distinct BCN networks 1730 and 1732 locatedabove the 5-42 upstream frequency band 1734 and cable TV 50-860frequency band 1736 are utilized. In this frequency plan, although onlytwo BCN Networks, 1730 and 1732, are shown, many more may be placedabove the ones shown in this frequency plan. Thus, it is shown that BCNnetworks may be located above or below traditional services in additionto being multiple BCN networks.

Turning to FIG. 18, multimedia access control (MAC) frame types 1800 aredescribed. A multiple layer protocol model may be employed with atransport layer encapsulating the MAC layer and carried in a physical(PHY) layer. The MAC layers 1802 may be made up of predefined packets orformats. The three top-level types of MAC transmission packets that mayoccur within the BCN Network 300 are; Data/control packet transmissions1804 (performed by both the Network Coordinator (NC) node and clientnodes), Beacon transmissions packet 1806 (performed by NC node) andProbe transmissions packet 1808 (scheduled by the MAC layer buttransmitted by another layer).

The data/control packet 1804 may have a hundred and sixty bit headerfollowed by a variable length payload and then a thirty-two bit cyclicredundancy checking (CRC). The payloads, for example, may be eithercontrol payload 1810 or data payload 1812. The data payload 1812 may beMPEG type data 1814 (MPEG, MPEG-2, MPEG-4, etc. . . . ), data protocols1816, such as Ethernet, or vendor defined data messaging 1818 thatsupports audio, video, data, or a combination of audio, video and data.

The control payload 1810 may be made up of MAP data 1820, reservationrequest 1822, link control 1824, and port-to-port control data 1826.Examples of MAP data 1820 that may be included as control payload 1810include isochroous MAP data 1828 or asynchronous MAP data 1830. Examplesof reservation request control payloads 1810 include messages to reservebandwidth for asynchronous communication 1832, channel probes 1834, andreserved bandwidth for port-to-port communication 1836. The port-to-portcontrol data 1826 may contain control information for the transmissionof MPEG type data 1838 and Ethernet 1840.

The link control 1824 payload may contain link probe A/D response 1842,admission request 1844, admission response 1846, key distribution 1848,dynamic key distribution 1850, link probe A/D request 1852, robustacknowledgement 1854, vendor proprietary link control payload 1856, linkprobe parameters 1858, power adjustment 1860, power adjustment response1862, power adjustment acknowledgement 1864, and power adjustment update1866. In other implementations, other types of link control payload datamay be defined and used in control packets 1810.

The beacon packet 1806 may be a packet that is 216 bits in length withan additional 32 bits of CRC data. When a BCN modem is activated, itattempts to locate the network timing by receiving a beacon packet 1806which identifies network timing and essential network controlinformation including network admission area, and other informationidentifying the time location and characteristics of other important andvalid information such as future beacon locations, future channelassignment information, etc. Any BCN modem that wishes to be admitted tothe network then transmits an admission request 1844 in a data/controlpacket 1804 to the NC using the identified admission area.

A probe packet 1808 may be generated by the physical layer and be usedto optimize and to verify each link in the network, such as link probe A1868, link probe B 1870, link probe C 1872, and link probe D 1874. Morespecifically, the probe packet 1808 may be used for at least threefunctions in a BCN network 310: link optimization, hardware calibration,and requesting a time slot to be allocated by a NC that may be used by aBCN modem to send packets to itself. In other implementations,additional probe packet payloads may be defined for the additional linkconfiguration and optimization.

In FIG. 19, a general format of an example header portion 1900 of theMAC control/data packet 1804 of FIG. 18 is shown. The header 1900 may beof a fixed length and consists of a transmit clock time stamp 1902, type1904 and subtype 1906 of the packet, a version identifier for MAC format1908, identification of the source BCN modem 1910 and the destinationBCN modems 1912, length of the packet 1914, a reserved area 1916 and aheader check sequence 1918 such as a CRC. In other implementations, theheader portion of the MAC control/data packet may contain additionalfields or few fields (i.e., no reserved area 1916). Further, the size ofthe fields may vary in different implementations.

The payload of a MAC packet 1804 may vary in length from 0 to 16 KB. Thespecific size is dependent on the packet type 1904 and packet subtypefields in the MAC packet header 1900. In the current implementation, ifthe payload length is zero, then there is no payload or CRC followingthe MAC Packet Header 1900. If the payload length is between 4B to 16KB, the last 4 bytes of the payload will contain the 32-bit CRC. The32-bit CRC covers the entire payload, but the 32-bit CRC does not coverthe MAC Packet Header. Also in the current implementation, payloadlengths of 1, 2 and 3 bytes may not be allowed.

In some implementations, multiple payloads may be nested inside aprimary payload. This is commonly referred to as Concatenation and maybe indicated by a flag in the MAC Packet Header (not shown).Concatenation is useful to gather multiple smaller payloads (e.g.,Ethernet packets) into a single transmission, which greatly increasesefficiency within the network.

Turning to FIG. 20, a media access plan (MAP) protocol data unit (PDU)that is continued in the payload part of a MAC control packet 1804 ofFIG. 18 is shown. The MAP PDU 1820 is one of four possible control PDUs(MAP PDU 1820, Reservation request PDU 1822, link control PDU 1824, andport-to-port message PDU 1826). The MAP PDU 1820 may be used to conveyinformation between BCN modems regarding upcoming transmissions. Thereservation request PDU 1822 may be used to obtain transmissionbandwidth. The link control PDU 1824 may be used to ensure efficientoperation of the BCN network. The port-to-port message PDU 1826 may beused to compliment data flows by exchanging information associated withproviding quality of service within the network. The packet type field1904 of the MAC header 1900 indicates the presence of one of the controlPDUs 1810.

Two types of MAP PDUs 1820 are possible in the BCN: isochronous 1828 andasynchronous 1830. Isochronous MAP PDUs 1828 are used to conveyinformation regarding transmission times of isochronous data flow.Asynchronous MAP PDUs 1830 are used to convey information aboutscheduled transmissions on the medium.

In FIG. 20, an asynchronous MAP PDU 1830 of FIG. 18 with a fixed-lengthPDU 2000 is shown. The fixed-length PDU 1830 consist of the followingfields: asynchronous MAP header 2002, followed by one or more allocationunits (AUs) 2004, 2006, 2008, belonging to one of the followingtypes—Asynchronous MAP AUs, Probe AUs, and NACK AUs. Each of the AUs mayhave null bytes that may be used to pad the MAP PDU 2000 to a fixedlength. In other implementations, the asynchronous MAP PDU 1830 may beof variable length, but additional processing would be required forformatting and decoding the PDU. Further, the probe AUs are used toallocate transmission opportunities to probe transmissions and theasynchronous MAP AUs 2004; 2006, 2008 may be used to allocatetransmission bandwidth to MAC control/data packet 1804 transmissions.

Turning to FIG. 21, an asynchronous MAP PDU header 2100 of theasynchronous MAP PDU of FIG. 18 is illustrated. The asynchronous MAP PDUheader 2100 may be a fixed-length header with a length of 224 bits. TheMAP PDU header 2100 may include a system time from which the MAP isvalid 2102, system time to which the MAP is valid 2104, parameters suchas encryption flags 2106, state information 2108, bit masks 2110, Nodeidentification for probe messages 2112, and miscellaneous data 2114.

In FIGS. 22A&B, the format 2200 of an asynchronous MAP allocation unit1830 is illustrated. Each allocation unit 1830 provides informationabout the start time and type of transmission scheduled along with themodulation scheme to be used and the source and destination BCN modemsfor the transmission. The format 2200 may include a type field 2202,subtype field 2204, source node identification 2206, destination nodeidentification 2208, modulation identification 2210, type of probetransmission 2212, identification of source node 2214, destination nodeidentification 2216, training bits 2218, miscellaneous bits 2220, andprobe data and offsets 2222.

Turning to FIG. 23, an illustration of the format of a NACK allocationunit 2300 is shown. These NACK allocation entries are used to provideinformation to requesting BCN modems and include reasons why the NC BCNmodem did not allocate bandwidth to their pending requests. The use ofthe NACK allocation units 2300 may be optional in some implementations.The NACK allocation unit 2300 may include reason code 2302,identification of original requesting BCN modem 2304, sequence number2306, type of original request being NACKed 2308, and subtype 2310.

Turning to FIG. 24, an illustration of a reservation request PDU 1822 isshown. BCN modem devices in a BCN network to request transmission timesuse the reservation request PDU 1822. An example of a reservationrequest PDU may include a reservation header 2402 and request elements2404, 2406, 2408. The request element portion of the request PDU 1822may be of variable length. In other implementations, the request elementportion may have a predetermined fixed length which is maintained withpadding bits. The following types of reservation request PDUs 1822 maybe used in a BCN network to make a reservation for isochronous data,asynchronous data, link probe, link control, and port-to-port messages.

In FIG. 25, an illustration of the format 2500 of the request PDU 1822of FIG. 24 is shown. The format 2500 may include an identifier 2502 ofthe number of request elements in the payload, miscellaneous data 2504,reserved bits 2506, state data 2508, and type of request elements 2510.In other implementations, fewer or additional fields may be used in arequest PDU.

In FIG. 26, an asynchronous data reservation request element 2600 usedin the format 2500 of FIG. 25 is illustrated. The asynchronousreservation requests may be sent by a requesting BCN modem to the NC BCNmodem to reserve bandwidth for transmission of asynchronous data. Theasynchronous data reservation request element 2600 may include a typefield 2602, destination field 2604, profile field 2606, sequence numberassociated with the request 2608, other parameters 2610, and a bandwidthrequest field 2612.

Turning to FIG. 27, a link probe reservation request element 2700 usedin the format 2500 of FIG. 25 is illustrated. The link probe reservationrequests are sent by a requesting BCN modem the NC BCN modem in order toreserve bandwidth for a probe transmission. The link probe reservationrequest element 2700 may include a type field 2702, reserved bits 2704,destination field 2706, index of the probe request 2708, identificationof the request 2710, profile field 2712, additional reserved bit field2714, and transmission time required 2716. The identification of therequest 2710 may be incremented every time a link probe reservationrequest is granted by the NC BCN modem. Further, the transmission timerequired 2716 may be a representation of predefined units, such as 20nanoseconds in the current implementation.

In FIG. 28, a link control reservation request element 2800 used in theformat 2500 of FIG. 25 is shown. The link control reservation requestsare used to reserve bandwidth for transmitting link control packets1824. The link control reservation request element 2800 may have a typefield 2802, subtype field 2804, destination BCN modem identification2806, profile for transmission 2808, sequence number associated with therequest 2810, reserved bits 2812, and required transmission time 2814.The required transmission time 2814 may be a representation ofpredetermined units, such as 20 nanoseconds used in the currentimplementation.

In FIG. 29, an illustration of the format 2900 of the link probe reportPDU of FIG. 18 is shown. Link control PDUs are used to maintainconnectivity among all BCN modems in a BCN modem network to ensure anacceptable quality of service (QOS) operation of the BCN network. A linkprobe report may be sent in a MAC packet of Packet type link-control1824 and Packet_subtype Link probe A/D report. This descriptor includesinformation regarding source and destination nodes, various settingsused for unicast transmission on the channel, transmit power controlparameters and reports usable constellation for each subcarrier of thesignal transmission. The fields of the format 2900 may include anidentifier of the number of source-destination pairs in the nextiteration 2902, source identifier 2904, destination BCN modem identifier2906, BCN NC relay data 2908, miscellaneous data 2910, Source BCN modem2912, destination BCN modem 2914, profile data 2916, along with otherdata.

Turning to FIG. 30, an illustration of an admission request PDU 1844 ofFIG. 18 is shown. A new BCN modem wishing to join the BCN network sendsan admission request PDU 1844 to the NC BCN modem. This request may besent using diversity mode transmission. The admission request maycontain data fields for node protocol support 3002, reserved bits 3004,MAC address of the BCN modem 3006, and transmit power adjustment 3008.The transmit power adjustment 3008 may be a decimal number between zeroand 63 which indicates the power adjustment value in units of dB to beused by the NC BCN modem for subsequent transmissions the BCN modem.

In FIG. 31, an illustration of an admission response PDU 1846 of FIG. 18is shown. The admission response PDU 1846 is sent by the NC BCN modem toa BCN modem that is being admitted to the BCN network. The fields of theadmission response PDU may include data fields for the total number ofBCN modems or nodes in the network 3102, a reset flag 3104, reservedbits 3106, maximum value of transmit power 3108, iteration data 3112,additional reserved bits 3114, protocols supported 3116, changes tofollowing reserved field 3118, and device identification of the BCNmodem 3120. In FIG. 32, an illustration of the format of a keydistribution PDU1848 is shown.

Turning to FIG. 33, an illustration of the format of the link probereport request PDU 1852 of FIG. 18 is shown. This link control payload1824 is used by BCN modems to request from other BCN modems a responseto the previous A or D type of link probe transmission. The format ofthe link probe report request PDU 1852 may include fields for source ofthe report 3302, destination of the report 3304, reserved bits 3306,relay flag 3308, and additional reserved bits 3310.

In FIG. 34, an illustration of the format of a general linkacknowledgement PDU 3400 is shown. The general link acknowledgement PUD3400 is a general-purpose acknowledgement payload used at the link layerto acknowledge various requests and operations.

In FIG. 35, an illustration of the link probe C parameters PUD 3500 isshown. The link probe C parameters PDU is sent by a node wishing toreceive a C type of probe. This packet is sent to the transmitter of theprobe to specify the details of the probe signal to be transmitted.Further example PDUs are power adjustment control PDU FIG. 36, poweradjustment response PDU FIG. 37, power adjustment acknowledgement PDUFIG. 38, and power adjustment update PDU FIG. 39.

In FIG. 40, an illustration of an Ethernet data payload 1840 of FIG. 18is shown. Ethernet data payloads are inserted into the MAC payload fieldaccording to an IEEE 802.3 frame without its FCS. The length of theEthernet data payload field is the length of the MAC packet as indicatedin the packet header minus the packet CRC and optional timestamps, ifpresent. Other protocols may be transferred in a similar manner asEthernet data, for example, MPEG data, frame-relay data . . . .

Turning to FIG. 41, a beacon packet 1806 of FIG. 18 is shown. The Beaconpacket may be a fixed length packet with a format that includesinformation elements 4102, reserved bits 4104, network information 4106,reserved bits 4108, BCN modem ID of the NC 4110, next beacon index 4112,reserved bits 4114, admission frame length 4116, asynchronous MAP length4118, isochronous MAP length 4120, admission window 4122, admissioncontention index 4124, asynchronous MAP profile 4126, asynchronous MAPindex 4128, isochronous profile 4130, isochronous index 4132, and CRC4134.

Security of data transmitted in the BCN network is provided to assureprivacy of transmitted data. The signals in the BCN network aretransmitted on the home coax network and may be detectible in homes thatshare the same multi-tap or are connected to an adjacent multi-tap.Without the use of a blocking filter such as, a “goober,” it is possiblethat neighbors could attempt to maliciously eavesdrop on another's BCNnetwork traffic. In order to prevent this type of eavesdropping, the BCNnetwork provides a privacy feature, which inhibits eavesdropping.

Privacy procedures encrypt all packets transmitted on a BCN network(i.e., the Home Video Network (HVN)) with a 56-bit DES encryption. Auser enters a password, which is used to distinguish between differentHVNs. The password is basically used to derive keys and authenticate BCNmodems. Once a BCN modem is authenticated, it is admitted with nofurther requirements. BCN modems with the same password will form oneHVN and nodes with different passwords will form separate HVNs.

In the BCN network, privacy procedures also help distinguish nodes whichshould locate themselves on different RF channels. Nodes with differentpasswords will not locate themselves on the same RF channel because theywill not be able to decrypt each other's messages. Instead they will seeeach other's transmissions as interference on the cable and thusautomatically locate themselves on different channels.

Privacy procedures may use both static and dynamic keys for encryption.The static keys are used for authentication and initial key distributionwhile the dynamic keys are used for subsequent key distribution andtraffic. Generation and distribution of dynamic keys are controlled by aBCN modem designated as the Privacy Master, which may also be the NC BCNmodem.

The password may be used to derive two static keys, which are used forencrypting MAC Management Messages and initially distributing dynamickeys. These static keys are called the MAC Management Key (MMK) andInitial Privacy Management Key (PMKInitial). BCN modems that have thecorrect MMK and PMKInitial will be able to communicate with the PrivacyMaster, receive dynamic keys, and join the HVN.

The two dynamic keys may be used for encrypting the Privacy Managementmessages and BCN modem traffic. These keys are the Privacy ManagementKey (PMK) and Traffic Encryption Key (TEK) respectively. PMKs and TEKsare generated and distributed to all other nodes by the Privacy Master.PMKs and TEKs are changed periodically.

There are five levels of attack that BCN modem privacy must consider:Simple Manipulation, Casual Hacking, Sophisticated Hacking, UniversityChallenge, and Criminal Enterprise. The same attack levels may begeneralized to the BCN network, which provides protection against SimpleManipulation, Casual Hacking, and Casual Hacking with help fromSophisticated Hacking, by link security in the BCN network fortransmitted data.

All encrypted BCN modem messages may be encrypted using DES Cipher BlockChaining (CBC) mode. In other implementations, 128-bit strong encryptionmay be employed. Encryption blocks must be aligned so that the beginningof the first 64-bit DES block is aligned to the first byte of the BCNmodem packet. Chaining is reinitialized on each BCN modem packet.Fragments of less than 64 bits at the end of a packet are encryptedusing residual termination block processing. Note that all BCN modempackets must contain an integer number of bytes and because of the 144bit BCN modem header will contain at least two DES encryption blocks.Given a final block having n bits, where n is less than 64, thenext-to-last ciphertext block is DES-encrypted a second time, using theECB mode, and the least-significant n bits of the result are exclusiveOR-ed with the final n bits of the payload to generate the short finalcipher block.

An alternative description of this procedure is that given a final blockhaving n bits, where n is less than 64, the n bits are padded up to ablock of 64 bits by appending 64-n bits of arbitrary value to the rightof the n payload bits. The resulting block is DES-encrypted using theCFB64 mode, with the next-to-last ciphertext block serving as aninitialization vector for the CFB64 operation. The leftmost n bits ofthe resulting ciphertext are used as the short cipher block.

The alternative description produces the same ciphertext. In thealternative description, however, no mention is made of combining ECBencryption with exclusive-OR-ing. These operations are internal toCFB64, just as they are internal to CBC. The alternative description isconvenient here because it allows residual block processing to beillustrated using CFB64 examples in [FIPS-81]. CBC mode provides moreprotection against attacks but can introduce error propagation. However,since a BCN modem provides a high availability network, the impact oferror propagation would be small.

A 64 bit Initialization Vector (IV) used with all encrypted packets isfixed and must be; IV=0×AA-AA-AA-AA-AA-AA-AA-AA. The IV may not betransmitted and is known a priori by both the encryption and decryptionBCN modem or other network devices. This is not a security risk becauseall BCN modem messages include a 32 bit transmit time at the beginningof the message which changes with every message. This creates the sameeffect as a dynamic IV.

A user-entered password may be used to control access of BCN modems to aHVN. BCN modems that have the same password will form one HVN while BCNmodems with different passwords will form separate HVNs. Passwords maybe manually entered by the user and typically will be the same for alldevices, which the user wants to be part of the same HVN. Therefore, itis expected that the user will go around his home and enter the samepassword into every BCN device in the current implementation. In otherimplementations, different HVN membership schemes may be employed (suchas IP address, MAC address, Portions of address, etc. . . . ).

Although the layout of a graphical user interface (GUI) and otherdetails of how passwords are input to a BCN modem are not shown, eachimplementation preferably will be capable of accepting a number up to 17digits long as the password for the BCN network. The GUI shouldencourage users to enter 17 digit random passwords for maximumprotection. If a password that long cannot be entered, it should bepre-pended by numerical zero (“0”) to make it into a 17 character ASCIIstring that is then used to produce a password seed in the currentimplementation. In order for devices to interoperate, passwords enteredon GUI using different methods should result in the same value of forthe password seed. In other implementations, other approaches topassword seed generation may be used.

In FIG. 42, a flow diagram of password generation in a BCN network isshown. The implementation specific password application, such as GUIwith alphanumeric input capability, accepts the password from a user4202. The format of the password is converted to a predeterminedstandard 4204. The formatted password is then used to compute thepassword seed 4206. The password seed then results in a PMK value 4208and a MMK value 4210. Upon calculating the password seed, the passwordmust be destroyed from local memory so that reading host memory cannotdiscover it. The password seed should persist through power cycles toensure that multiple BCN modems may come up and restore communicationwith each other through power failures.

The process and messaging shown may be performed by hardware orsoftware. If the process is performed by software, the software mayreside in software memory or memories (not shown) in the BCN network.The software in software memory may include an ordered listing ofexecutable instructions for implementing logical functions (i.e.,“logic” that may be implemented either in digital form such as digitalcircuitry or source code or in analog form such as analog circuitry oran analog source such as an analog electrical, sound or video signal),may selectively be embodied in any computer-readable (or signal-bearing)medium for use by or in connection with an instruction execution system,apparatus, or device, such as a computer-based system,processor-containing system, or other system that may selectively fetchthe instructions from the instruction execution system, apparatus, ordevice and execute the instructions. In the context of this document, a“computer-readable medium” and/or “signal-bearing medium” is any meansthat may contain, store, communicate, propagate, or transport theprogram for use by or in connection with the instruction executionsystem, apparatus, or device. The computer readable medium mayselectively be, for example but not limited to, an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatus,device, or propagation medium. More specific examples, that is “anon-exhaustive list” of the computer-readable media, would include thefollowing: an electrical connection (electronic) having one or morewires, a portable computer diskette (magnetic), a RAM (electronic), aread-only memory “ROM” (electronic), an erasable programmable read-onlymemory (EPROM or Flash memory) (electronic), an optical fiber (optical),and a portable compact disc read-only memory “CDROM” (optical). Notethat the computer-readable medium may even be paper or another suitablemedium upon which the program is printed, as the program can beelectronically captured, via for instance, optical scanning of the paperor other medium, then compiled, interpreted or otherwise processed in asuitable manner if necessary, and then stored in a computer memory.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof this invention.

1. A Broadband Cable Network (BCN) modem having a transmitter thattransmits packets to a plurality of nodes in a broadband cable network,the transmitter comprising: a MAC subsystem that provides the packetsfor transmission within the broadband cable network; a Modem subsystemin signal communication with the MAC subsystem, the Modem subsystemreceiving the packets from the MAC subsystem and appending informationto the packets; and a RF subsystem in signal communication with theModem subsystem, that receives the packets from the Modem subsystem andupconverting the packets received from the Modem subsystem; wherein atleast one of the packets is a beacon packet that has a channel numberfield, change field, sequence number field, network coordinator IDfield, next beacon index field, admission frame length field, admissionwindow, asynchronous MAP length field and a beacon Cyclic RedundancyChecking (CRC) field; and wherein at least one of the packets is a dataand control packet having a header and a variable length payload andwherein the header has at least five fields selected from the groupconsisting of a transmit clock field, packet type field, packet subtypefield, version field, source node ID field, destination node ID field,and header check sequence field.
 2. A Broadband Cable Network (BCN)modem having a receiver that receives packets from a plurality of nodesin a broadband cable network, the receiver comprising: a RF subsystemthat receives packets and downconverting the packets wherein at leastone of the packets is a control and data packet having a header, theheader having at least five fields selected from a group consisting of atransmit clock field, packet type field, packet subtype field, versionfield, source node ID field, destination node ID field, and header checksequence field, the control and data packet further having a variablelength payload; a Modem subsystem in signal communication with the RFsubsystem, the Modem subsystem receiving the packets and removingcontrol information from the packets; and a MAC subsystem that receivespackets within the broadband cable network and retrieving data for useby the BCN modem; wherein at least one of the packets is a beacon packetthat has a channel number field, change field, sequence number field,network coordinator ID field, next beacon index field, admission framelength field, admission window, asynchronous MAP length field and abeacon Cyclic Redundancy Checking (CRC) field.
 3. A method fortransmitting packets from a Broadband Cable Network (BCN) modem to aplurality of nodes in a broadband cable network, the method comprising:formatting the packets in a MAC subsystem that transmits the packetswithin the broadband cable network, including formatting a data andcontrol packet for transmission within the broadband cable network, thedata and control packet having a header and a variable length payload,the header having at least five fields selected from the groupconsisting of a transmit clock field, packet type field, packet subtypefield, version field, source node ID field, destination node ID field,and header check sequence field; receiving the packets from the MACsubsystem at a Modem subsystem that is in signal communication with theMAC subsystem and that appends information to the packets; andupconverting the packets with the information for transmission via thebroadband cable network at a RF subsystem that is in signalcommunication with the Modem subsystem; wherein at least one of thepackets is a beacon packet that has a channel number field, changefield, sequence number field, network coordinator ID field, next beaconindex field, admission frame length field, admission window,asynchronous MAP length field and a beacon Cyclic Redundancy Checking(CRC) field.
 4. A method for receiving packets at a receiver in aBroadband Cable Network (BCN) modem from at least one node in abroadband cable network, the method comprising: receiving the packetsand downconverting the packets at a RF subsystem including a control anddata packet having a header that has at least five fields selected fromthe group consisting of a transmit clock field, packet type field,packet subtype field, version field, source node ID field, destinationnode ID field, and header check sequence field and variable lengthpayload; removing control information from the packets in a Modemsubsystem that is in signal communication with the RF subsystem; andretrieving data for use by the BCN modem at a MAC subsystem that is insignal communication with the Modem subsystem and in receipt of thepacket with the control information removed; wherein at least one of thepackets is a beacon packet that has a channel number field, changefield, sequence number field, network coordinator ID field, next beaconindex field, admission frame length field, admission window,asynchronous MAP length field and a beacon Cyclic Redundancy Checking(CRC) field.